Elsevier

Food Quality and Preference

Volume 18, Issue 6, September 2007, Pages 901-908
Food Quality and Preference

Impact of ethanol on the perception of wine odorant mixtures

https://doi.org/10.1016/j.foodqual.2007.02.004Get rights and content

Abstract

Several studies have focused on perceptual interactions in binary odor mixtures, but few on more complex mixtures. The aroma of wine is an example of a complex odor mixture. Our aim was to assess the impact of ethanol on the perception of mixtures of Woody (whiskey lactone) and Fruity (isoamyl acetate) odorants commonly found, physico-chemically and perceptually, in wine. Physico-chemically, reduced whiskey lactone volatility was observed in hydro-alcoholic solutions. Perceptually, a synergy effect by the Woody on the Fruity odor was observed in aqueous solutions, which disappeared with the addition of ethanol. Conversely, the Woody odor was masked in both aqueous and dilute alcohol solutions. In addition, mixed Woody and Fruity odors were found to mask the so-called Alcohol odor. These results underline the importance of perceptual interactions in the perception of wine bouquet.

Introduction

The emergence of new consumption trends, the constant drop in regular wine consumption and the development of a worldwide structural surplus are known to have faced the wine industry with a wide range of problems (Descout et al., 2003). Moreover, the harmful effects of alcohol on health and behavior have led several countries to regulate the consumption of alcohol, with age limits required for the purchase of alcohol or maximum permitted alcohol blood levels for driving. Another harmful effect of alcohol, mediated by lactating mothers, is on breastfed infants (Little et al., 2002, Mennella and Beauchamp, 1991).

All these consequences of alcohol consumption have led researchers and wine growers to seek to design low-alcohol wines, which could let consumers continue to enjoy wine-drinking, while avoiding the harmful effects of ethanol. One difficulty here is to maintain the aromatic bouquet of the wine, while reducing the alcohol content; few studies, however, have looked at the perceptual impact of alcohol content on the perception of wine flavor.

In 1994, Fischer and Noble studied 18 wines varying in ethanol content (8%, 11%, 14% v/v), pH (2.9, 3.2, 3.8) and (+)-catechin level (100 and 1500 mg/L). Twenty panelists assessed sourness and bitterness intensities. The results showed that an increase in ethanol content raised bitterness intensity but had only a slight effect on sourness. Martin and Pangborn, 1970, Vidal et al., 2004 observed the same effect of ethanol on bitterness. Similarly, according to Mattes and DiMeglio (2001), who worked on the oral ethanol exposure effect on ratings for sucrose, NaCl, citric acid and quinine hydrochloride, ethanol enhanced the bitter aftertaste of quinine although it suppressed its bitter character when held in the mouth. Furthermore, according to these authors, ethanol itself has a bitter taste at concentrations near threshold. Martin and Pangborn (1970) also observed that alcohol slightly enhanced the sweetness of sucrose and depressed the perceived intensity of salt and sourness.

Few studies have been performed on aroma aspect and possible perceptual interactions between wine aroma compounds in mixtures of more than two odorants (Escudero et al., 2004, Lorrain et al., 2006), although there have been some studies of a simpler model using binary mixtures. Thus, Atanasova, Thomas-Danguin, Chabanet et al. (2005) highlighted perceptual interactions in binary supra-threshold mixtures of Woody and Fruity wine odorants. The odor quality of the mixtures was found to be perceived as mainly homogeneous, with a perceptual dominance of the Woody odor for iso-intense mixtures; interactions depended on the perceived intensity of each component. Another study notably found that a sub-threshold Woody component enhanced the Fruity odor (Atanasova, Thomas-Danguin, Langlois et al., 2005). In more complex mixtures, a previous study by Moio, Schlich, Issanchou, Etiévant, and Feuillat (1993) showed that when the Woody odor raises in a wine, the complexity, and particularly the Fruity and Floral components of the bouquet is reduced.

Furthermore, it is important to notice that temperature is an important parameter that could affect wine bouquet. Indeed temperature is particularly important for wine drinkers, and often impacts on the perception of odorants mixtures. Whelton and Dietrich (2004) especially found that odor intensity was a function of both aqueous concentration and water temperature for water containing several odorants.

Concerning the impact of ethanol on aroma perception, Pet’ka, Cacho, and Ferreira (2003) used wine-tasting and GC–O procedures to assess the perceptual intensity of eight aroma compounds, chosen as examples of chemical groups relevant to wine flavor research, at three suprathreshold concentrations, with the same intensity scale. The results showed that ethanol has an additive effect on intensity and that adding ethanol at a low concentration (under 10%) could decrease aroma compound detection thresholds. More recently, Grosch (2001) observed that the less ethanol in a complex wine model mixture, the greater the intensity of the Fruity and Floral odors; this could be due to increased partial pressure of the odorants with reduced ethanol concentration.

Thus, ethanol modifies the perception of wine aroma compounds, but it remains to be established whether this impact is only physico-chemical or also perceptual. Atanasova, Thomas-Danguin, Chabanet et al. (2005) demonstrated perceptual interactions between Fruity and Woody components but did not study their impact with ethanol, a major aroma compound in wine. The present study therefore sought to assess the impact of ethanol in both physico-chemical and perceptual terms: i.e., on the volatility of Woody and Fruity aromas and on their olfactory perception, alone and in mixtures.

Section snippets

Odorants

Two wine odorants were chosen to give a simple model solution of wine aroma. One of these components, β-methyl-γ-octalactone (generally called whiskey lactone), is mainly brought by oak wood, and was described as “Woody-Coconut”; the other is an ester, isoamyl acetate, described as “Fruity-Banana”. Two types of mixture were studied: the first combined the two odorants at four concentrations in an aqueous solution (MilliQ system, Millipore®, France); the second combined them at four

Physico-chemical analysis

The first analysis was intended to check for any physico-chemical impact of adding ethanol on the gas-phase concentrations of whiskey lactone and isoamyl acetate. To assess the impact of ethanol on gas-phase odorant release, we sought to obtain the same gas-phase concentration in both the dilute alcohol and aqueous solvents, changing the concentration only in the liquid phase. This matching procedure was intended to clarify the subsequent sensory analysis. The gas- and liquid-phase

Conclusion

Physico-chemical and perceptual interactions between Woody and Fruity odors in aqueous and dilute alcohol solutions were studied under laboratory conditions using physico-chemical and psychophysical methods. The physico-chemical results showed both chemical and sensory interactions between the three components. There was a significant difference in whiskey lactone (Woody component) volatility between the aqueous and the dilute alcohol solutions, which did not seem to be the case for isoamyl

Acknowledgements

This work was carried out with the financial support of INRA, the Burgundy Regional Council and the “Agence Nationale de la Recherche” under the “Programme National de Recherche en Alimentation et nutrition humaine”, Project “ANR-05-PNRA-011, VDQA”.

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